Celtic and Rangers fans taunt one another at an Old Firm game this year. Photograph: Carl Recine/Action Images

All the police cells were full across the city, with some of those arrested having to be ferried to police stations up to 50 miles away. A wild west-style brawl enveloped one Glasgow southside pub, leaving 10 officers injured. There were other outbursts of aggression too, not just in bars and on streets but in homes. In the hours after the final whistle was blown, domestic violence reportedly rose by 81%.

The disorder, which broke out in mid-February after one of the city's famous Old Firm matches - between arch rivals Rangers and Celtic - led to Les Gray, head of the Scottish Police Federation, calling for the derbies between the two clubs to be banned. The football, he said, was not worth the " murder and mayhem" the games unleashed.

Last Wednesday, trouble erupted again, at the third match between the two clubs in less than a month, on andoff the pitch once more. Players shared a total of 13 yellow cards, most shown to Rangers players, with three sent off – one of a record seven between the rivals this season.

There were 34 fans arrested inside the Parkhead grounds after extraordinary scenes between Celtic manager Neil Lennon and Rangers assistant manager Ally McCoist, when both men had to be restrained. There is still furious speculation among fans about what words were exchanged between the two who have since shaken and made up according to Lennon who said only: "It's a passionate game and both of us want our teams to win." But now, after it was revealed this weekend that Lennon had been given 24-hour security protection, after a second hoax bomb package in as many months was intercepted on the way to his home, Scotland's first minister, Alex Salmond, has called an emergency summit this week in Edinburgh to discuss the problems. The great fear is that the sectarian violence of the past could once again rear its head in a city that is riven by religious prejudice.

In the east end of Glasgow yesterday, the refrain followed a familiar pattern. A stream of Celtic fans heading for a match against Hamilton blamed the problems on aggression on the pitch by Rangers players. Just as the Rangers fans blame Neil Lennon.

At Baird's Bar, Celtic fans without tickets prepared for the match to start on TV with several dozen pints and some noisy Irish jigs. A busload of Irish supporters from Co Meath, who got up at 4.30am to catch their ferry over, were stopping by. Chris Millar, 36, was also over for the match. "Both Rangers and Celtic need to grow up," he says. "We're in big danger of going back to the sectarian dark ages. At the end of the day, it's a football game."

Landlord Thomas Carberry has a sign on the wall that promises zero tolerance to IRA songs. The two fans outside having a song with their cigarettes clearly have not read it. The pub is plastered with Celtic and Irish memorabilia. Carberry is worried by police suggestions that pubs might be asked to close during Old Firm matches. "It's all the trade we get around here. The smoking ban, the cheap supermarket booze, the recession – it's all taking its toll," he says.

"The whole east end is reliant on these matches. This city is divided and you're not going to change that. It's deep; it's even in the clothes. You can't wear a blue top and get away with it in some places. I've got three Protestants working behind the bar here, but in other places the sectarianism is just rife, [in] the city council for a start. My opinion is that the schools need to be mixed. Until you do that, you won't change anything. Until then what we have is a healthy bit of bitterness that keeps us all going."

Many fans on both sides insist the divides are misunderstood and that often the banter that flares during the match is forgotten afterwards. "I hate them for those 90 minutes, and it's reciprocated," said Paul Cassidy, a 44-year-old Glaswegian Celtic supporter. "But all that aside, it's the drinking, the blokes tanking it in pubs all day and fuelled up and going home and beating up their wives – that is something we should be looking at."

Many experts agree that social issues are important. Dr Susan Wiltshire, of Glasgow University, has just published a research paper commissioned by the Scottish parliament that looks at apparent prejudice in the justice system against Catholics. Some 17% of Scotland's population are Catholic, yet Catholics make up 26% of those in Scottish jails.

"My paper was about discrimination that Catholics in Scotland might experience in the criminal justice system and about poverty indicators, such as that Catholics are more likely to live in poorer areas, though again, there are strong historical settlement patterns which account, in part, for this. This is a social issue which should not be ignored," she says.

Wiltshire adds: "The Catholic-Protestant divide which often ignites at matches is so structurally entrenched that it is something that has to be addressed at various levels, and consistently and systematically. "

Wiltshire says that a drop in political commitment to tackling sectarianism is also apparent. One charity, Nil by Mouth, set up to tackle religious bigotry in schools, is facing closure because of cuts in its funding.

Bob Doris, the Scottish National party MSP for Glasgow, has written to Celtic and Rangers urging them to support the charity financially. He says: "Off-field trouble related to Old Firm games is a reflection of wider problems in society, male violence and alcohol abuse that would exist even if the Old Firm did not.

"That said, both clubs are well aware that their players are role models to many. The clubs don't share the blame for that disorder – people are responsible for their own actions – but they do shoulder a responsibility for helping to find a solution."

Alcohol, football, religion and discrimination all no doubt play a part in the sectarian issues facing Glasgow.

The Louden Tavern is five minutes' walk from Baird's. "Aye, but we get the cleaners in now and again," says Rangers fan Andy McMinigal, 55. "That pile of rubbish Baird's have got down there would go up if someone put a match to it."

He has come in with fellow Rangers season-ticket holder Charlie Watts, 63. They are in their suits after a Saturday morning Orange Lodge march. "Most pubs are not segregated as such, but they'll have a pope corner and a proddy corner but they still mix," Watts says.

"Keeping people apart you can blame on the Catholic Church. It's them that's wanting separate schools. The Catholics are separatists and criminals, it's just a fact of life. But with the football it's the young people who get tanked up on drugs and drink and just want to spoil it for everybody."

Landlord Robert Marshall keeps his colour scheme true blue. Blue walls are hung with portraits of Rangers' great and good.

"Its a Catholic lassie that does them," says Marshall, who took over what had been a loyalist pub in 1994. "I don't hold with any of that, I've never been to Ireland and I'm not interested. None of this sectarian stuff has anything to do with religion. That's just what the morons on both sides say. I hate Celtic but I don't hate Celtic supporters."

Several of the banners he has hung outside his pub over the years have had to be taken down because of the "lack of sense of humour" of Celtic fans who complained to police. "They were looking for an insult when there wasn't one. The thing about Glaswegians is, because of [the city's] working-class roots and its poverty through the years, there's a sense of humour that people can find heavy going, they think we're having this terrible fight.

"Look at those figures, 60,000 supporters in a city and there's only 50 odd extra arrests? The Rangers-Celtic thing is a lot of people's whole lives and we are a city who is passionate about football. Its just a normal city, a great city ... until there's an Old Firm game."